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Clarification on Remote Copy Groups and Source CPG's
https://3parug.net/viewtopic.php?f=18&t=3243
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Author:  MBILC [ Tue Jul 16, 2019 1:50 pm ]
Post subject:  Clarification on Remote Copy Groups and Source CPG's

Hello,

Just want to ask for some clarification before committing to something that may not be necessary.

Currently working on new datastores for our environment. We have 2 3PAR 7400 backends and existing remote copies. (SSD/FC/NL)

Due to some space constraints and still shifting data around, we have a lot of space in our SSD tier vs our FC tier on one of the 3PAR systems.

I have a CPG and AO set up that uses SSD and FC tier only. (Could say Gold Tier)

I have a Remote Copy Group that is set to copy from my Source User CPG of FC to the CPG of FC disks on the 2nd 3PAR system.

Now, I want to create some new Virtual Volumes under the same CPG as the existing VV already in the remote copy group. However, due to space limitations, i want to set the Default CPG to go to the SSD tier (temp, eventually tune it back to FC once space allows)

Because i want to set the Default CPG to SSD Tier for these new Virtual Volumes, do i need to set up a separate Remote Copy Group with the source user cpg as the SSD tier and destination as the SSD tier?

Or if i issue these new Virtual Volumes and just place it under the existing remote copy group, will it also grab data on the SSD tier as well?

Author:  MammaGutt [ Wed Jul 17, 2019 4:10 am ]
Post subject:  Re: Clarification on Remote Copy Groups and Source CPG's

Remote Copy group is a group of VVs replicating between 2 RC targets. Each VV (of both arrays) has its own set of configuration like User and Copy CPG.

So there is no requirement for all VVs in the same RC group to use the same CPGs.

Author:  MBILC [ Wed Jul 17, 2019 9:08 am ]
Post subject:  Re: Clarification on Remote Copy Groups and Source CPG's

Thank you MammaGutt, good to know.

Next question would be then, is there any benefit to having multiple RCG's vs say 1 big one for similar VV's ?

Since we only have 2 systems to replicate too and they are connected with 10G Fiber back end latency and speed between systems is not really an issue.

Author:  MammaGutt [ Wed Jul 17, 2019 1:11 pm ]
Post subject:  Re: Clarification on Remote Copy Groups and Source CPG's

MBILC wrote:
Thank you MammaGutt, good to know.

Next question would be then, is there any benefit to having multiple RCG's vs say 1 big one for similar VV's ?

Since we only have 2 systems to replicate too and they are connected with 10G Fiber back end latency and speed between systems is not really an issue.


There are pros and cons for everything. If you use CLX, you need each cluster resouce to have a dedicated RC group. If you have a big environment that xan quickly lead to a lot of RC groups making management complex and worst case hitting some maximum limit. On the other hand, putting everything into one means that if you need to switch the replication you have to do all volumes in one go which may increase both the time it takes to switchover and re-sync.

So hard to give an "one-size-fits-all" recommendation.

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